Can I block a number permanently on a child’s cell phone..that cannot be unblocked?

[Mumbear]

My underage daughter has been getting texts and calls from a boy, also underage but 4 years older. Highly inappropriate. I can block him on her phone but she unblocks him because she thinks he is a friend....but we see it as grooming behaviour. Can I block him within the account permanently so she cannot unblock?

[Matt2]

I’d tell the school of the boy to get a school officer to get him to stop. That’s just gross of him to prey on girls 4 years younger